1. Field of the Invention
This invention pertains to cylindrical counter-flow heat exchangers especially as used in cryogenic refrigeration systems.
2. Background of the Related Art
A cryogenic refrigeration system consisting of a combination of a displacer-expander refrigerator and a circulation loop with a Joule-Thomson valve and a cryogenic condenser is disclosed in U.S. Pat. No. 4,484,458. In such a refrigeration system, a counter-flow heat exchanger is used to exchange heat from a high-pressure, high-temperature fluid to a low-pressure, low-temperature fluid within the circulation loop. The counter-flow heat exchanger should be compactly arranged with the displacer-expander refrigerator, while heat loss should be minimized.
The counter-flow heat exchanger disclosed in said U.S. patent is a helical double-pipe wound around a refrigerator. A high-pressure fluid is introduced into the inner pipe, while a low-pressure fluid is introduced into the annulus region between the inner and the outer pipes. Such a double-pipe heat exchanger, however, is difficult to manufacture and does not have design flexibility with respect to variations in flow area and heat-transfer surface areas.
Another type of heat exchanger known as a laminated metal heat exchanger is also used as cryogenic counter-flow heat exchanger. High heat-conductivity plates and heat-insulating plates, both with holes for a high-pressure fluid and holes for a low-pressure fluid, are alternately stacked and bonded, so as to form separate high-pressure fluid paths and low-pressure fluid paths. This type of heat exchanger, however, is difficult to manufacture so as to provide complete sealing of the high-pressure fluid.